Table 1.
Selected studies targeting α-synuclein as biomarker for the diagnosis of PD.
| Ref | Materials | Analytical/measuring methods | Results in PD patients compared to controls |
|---|---|---|---|
| Lebouvier et al., 2008 [84] | Colonic tissue | Biopsy and immunohistochemical studies | TH-IR (tyrosine-hydroxylase immunoreactive) neurons were not a marker but phospho-α-synuclein-IR neurities were found in PD patients |
| Beach et al., 2010 [75] | Lower esophagus and submandibular tissue | Biopsy and a sensitive immunohistochemical method for phosphorylated α-synuclein | A rostrocaudal gradient of decreasing phosphorylated α-synuclein histopathology frequency and density |
| Shi et al., 2010 [45] | Alpha-synuclein in plasma | Blood component separation and analysis | No statistical difference was observed |
| Cersósimo et al., 2011 [85] | Salivary gland | Biopsy and immunohistochemical studies | The presence of α-synuclein inclusions in the submandibular glands |
| Devic et al., 2011 [76] | Saliva | Immunoblotting with a rabbit anti-human α-synuclein antibody ASY-1 | The level of α-synuclein decreased |
| Yanamandra et al., 2011 [77] | Alpha-synuclein reactive antibodies in blood sera | ELISA, western blot, and Biacore surface plasmon resonance | Higher antibody levels towards monomeric α-synuclein |
| Shannon et al., 2012 [86] | Colonic submucosa | Biopsy and immunohistochemical studies | Staining for α-synuclein in nerve fibers in colonic submucosa |
| Alexoudi et al., 2013 [87] | Submandibular gland | Topic discussion | Positive |
| Schmid et al., 2013 [88] | Alpha-synuclein posttranslational modifications (PTMs) | A new chemical synthesis scheme | Relevant PTMs associated with disease progression and severity |
| Adler et al., 2014 [89] | Submandibular gland | Biopsy and immunohistochemical studies | Microscopic evidence of the tissue was positive for Lewy type α-synucleinopathy |
| Gao et al., 2015 [46] | CSF | Meta-analysis | The mean CSF α-synuclein concentration was significantly lower |
| Sanchez-Ferro et al., 2015 [90] | Gastric mucosa samples | Biopsy and immunohistochemical studies | Positive fibers for the α-synuclein protein were observed |
| Zhou et al., 2015 [73] | CSF | Meta-analysis | Mean concentration of CSF α-synuclein was slightly decreased; mean concentration of CSF α-synuclein oligomers was significantly higher |
| Adler et al., 2016 [91] | Submandibular gland | Biopsy and immunohistochemical studies | Positive staining |
| Donadio et al., 2016 [83] | Skin nerve | Skin biopsy | Only 49% of samples with a higher positivity rate for abnormal α-synuclein deposits at the proximal site in IPD |
| Parnetti et al., 2016 [74] | CSF | Review of 32 selected articles | The role of α-synuclein species in PD prognosis remained unsatisfactory |